Doctor shape control device



Sept. 3, 1968 E. E.cR|s1' DOCTOR SHAPE CONTROL DEVICE Filed March 6, 1964 mflilgv INVENTOR '{mez 16.' C'

United States Patent() 3,399,420 i DOCTOR SHAPE CONTROL DEVICE Elmer E. Crist, Beloit, Wis., assgnor to Beloit Corporation, Beloit, Wis., a corporation of Wisconsin Filed Mar. 6, 1964, Ser. No. 349,963

1 Claim. (Cl. 15-256.51)

ABSTRACT F THE DISCLOSURE A roll with a doctor blade in close running relation supported on a doctor back having an elongate force member connected to each end of the doctor back with expansible bellows at the center of the force member applying a shape controlling force to the center of the doctor back.

The present invention relates to improvements in doctoring assemblies of the type used in papermaking and paper finishing machines and particularly to a doctor back in which the shape can be changed for controllably atecting the doctor blade pressure, and for changing the shape of the back to accommodate changes in roll contours.

The invention contemplates providing a doctoring assemblyl having a doctor back adapted for supporting a doctor blade for engagement with rolls of different contours wherein the back has pivotal supports at the ends for pivotally loading the back and holding the blade against a travelling surface. A tie rod is secured at its ends to the ends of the doctor back and extends non-parallel to the axis of the back, and a force applying member pref-y erably in the form of an inatable bellows is located at the center of the back engaging the tie rod and connected to a controlled pressure air line for varying the force applied tothe back and in effect varying the torce components at the center and ends of the back normal to the back axis for bending the back and obtaining a predetermined shape characteristic of the back relative to the roll.

In a doctoring operation in a paper machine a doctor blade is held against a travelling surface'of either a roll or a paper web supported by the roll. The mechanism of the present arrangement may be used in doctors for dryers, calenders or press rolls, or also may be used in coating doctors. In many operations the roll will be crowned and this crown may change with such a backing roll whichhas'v anti-deflection mechanism by which the crown of the roll can be changed or by a roll which is used in nip delining relationship with other rolls and the crown will change with change in nip load, such as in Va calender stack. ln coating mechanisms the angle between the doctor blade may be changed thereby changing the position of the doctor Vback and the eiect of its weight will then change its curvature. Proper doctor blade pressure alongits length is critically essential since it affects wear of the blade and it afects performance and operation. This is also true in doctoring operations involving coating wherein the quantity and-quality ,of coating'is controlled by-blade pressure'.

It is accordingly an object of the present invention to provide a doctoring assembly having a doctor back wherein its shape can be changed along its length `to obtain uniform lblade pressure regardless of the crown on the backing roll. Y l

A further object of the invention is to provide an improved and simplified doctor back inwhiclrthebowlalong its length can be changed controllably and simply and easily during operation.

A still further object of the invention is to provide a doctor back which can be changed in shape so as to be usable with backing rolls of diierent crowns or to be usable with a backing roll having an adjustable crown.

A still further object of the invention is to provide a doctor back for supporting a doctor blade for use with a roll which is subject to crown changes and subject to roll bending such as occurs with a plurality of rolls but may be used with a varying number of nips in a paper machine to cause changes in roll shape that could cause poor doctor tits and wherein the shape of the doctor back can be readily changed by automatic or manual adjustment.

Other objects, advantages and features will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiment thereof in the specification, claim and drawings, in which:

FIGURE 1 is a fragmentary elevational view shown in somewhat schematic form of a doctoring assembly constructed and operating in accordance with the principles of the present invention;

FIGURE 2 is a somewhat detailed elevational view, with parts broken away, of a doctor back assembly of the present invention;

FIGURE 3 is an enlarged detailed sectional View taken substantially along line III-III of FIGURE 2; and

FIGURE 4 is a schematic View showing the combination of a backup roll having a controlled crown with a doctoring mechanism.

On the drawings:

FIGURE 1 shows a backing roll 10 with a doctor blade assembly 11 having a doctor back 12 supporting a doctor blade 13 in close-running pressure relationship to a web W carried on the surface of the roll 10. The roll 10 may be subject to bending forces due to its weight, due to forces from other rolls forming pressure nips with the roll, or due to roll bending devices which apply forces so as to crown the roll. As these extraneous forces on the roll change the crown on the roll 10 changes. This will change the relationship between the doctor blade 13 and the roll 10 along its length adversely affecting uniform operation along the roll length. However, in accordance with the present invention the shape of the doctor back 12 can be changed to maintain constant pressure of thev doctor blade 13 against the backing roll 10 along its length with change in the shape of crown of the roll 10, or so that the doctoring assembly 11 may be used with rolls of diterent crowns.

The doctor blade 13 has a holder 15 which is supported in a seat 12a on the doctor back 12.

As illustrated in FIGURES l through 3, the doctor back 12 has a planar tlat blade supporting portion 12b with a blade carrying seat 12d. The at portion 12b is bent downwardly at its rear in a right angle portion 12e. For completing the doctor back, a plate 16 is secured beneath the at portion 12b by welding, and the plate 16 `backing roll 10 by suitable loading mechanism as will be fully appreciated by those versed in the art.

Extending through the channel 17 of the back is a tie rod 22 having ends which project through holes in the ends 18 andr19 of the doctor back. The ends of the tie rod are threaded to receive nuts 23 and 24 for securing the ends of the rod 22 in order that it can transmit forces to the ends of the doctor back.

Intermediate the ends of the doctor back, and illustrated as being at the center of the back in the preferred embodiment, is a force applying member having a saddle 25 for applying a force to the rod 22, and having a bellows 26. Bellows 26 at its upper end engages the flatrpor tion 12b. of the back, An inflatable bellows is a preferred form of force applying means, although other force applying devices may be employed. An air operated force applying means is preferred since the overall force can be easily varied by varying the air pressure. Also, while other fluid `operated force chambers may be used such as a piston and cylinder, -a resilient inatable bellows such as 26 is preferred since it is not subject to corrosion and is relatively inexpensive to obtain and maintain in operating condition.

An air line 27 leads through the channel 17 and is connected to a suitable air pressure supply, as shown in FIG- UR'ES 2 and 3. A controllable pressure regulator 28 is provided which may be either manually or automatically operated to vary the force applied by the `bellows 26.

The bellows thus applies a force normal to the axis of the back at the center thereof which is in an upward direction, as illustrated in FIGURES 2 and 3, and the tie -rod 27 provides non-extensible links leading to each end of the back, and the ends of the rod apply a force component in a downward direction which is normal to the axis of the back. Any pressure change within the bellows 26 will automatically and simultaneously change the force components at the center and the end of the back so as to change the bending force applied to the doctor back. As will be observed, the forces are applied normal to the axis of the doctor back, and normal to the plane of the blade 13.

For convenience of installing and servicing the bellows 26 an opening 32 is provided in the doctor back 12 in the rear portion 12C thereof. Surrounding the opening and rwelded to the outer surface of the doctor back 12 is a ange ring 33 for supporting a cover plate 39, The cover plate is held in place by cap bolts 38 threaded into tapped holes in the ring 33 and it may be readily removed or replaced. The cover plate has an opening 40 for the air pressure line 27.

For stabilizing the bellows 26 and preventing the saddle 25 from tipping a rod 37 extends laterally from a base 34 `of the bellows 25, and is threaded with lock nuts 35 and 36 securing the rod 37 to the cover plate 39. The outer nut 36 is of course removed when the cover plate 39 is removed.

FIGURE 4 illustrates a doctor blade assembly wherein the backup poll is engaged -by another roll 29 which forms a pressure nip N therebetween. The forces of the roll 29 will of course tend to crown the backing roll 10. The backing roll 10 is also supported on a support shaft 30 provided with roll deection control mechanism 31. The roll deection control mechanism may have spaced bearings, as indicated by the arrowed lines which apply forces to the shaft 30 to control the pressure along the nip N and control the elective crowning of the roll 10. The roll bending forces may be applied in various ways, and a mechanism, such as that shown in the Moore et al. -Patent 3,060,843, may be used by way of example. As the crown of the -r-oll 10 changes, due to forces applied thereto by the roll 29 and by the deection control mechanism 31, the curvature of the doctor back 12 can be changed accordingly by regulating the pressure in the bellows 26 so that a uniform pressure |will be obtained between the doctor Iblade -and the surface of the web in order to obtain uniform coating pressure.

In the arrangement of FIGURE 4, means may be employed for applying a controllably variable force to the roll 29. As this force is changed, usually the forces applied by the deection control members 31 will be changed and automatic mechanism may be employed which relates the two mechanisms for controlling the forces applied to the upper roll 29 and the shaft 30 of the lower roll 10. Automatic means may also be employed which relates the pressure in the bellows 26 to the pressure in the nip N (which is a function of the forces applied to the rolls 29 and 10). In other words, the bellows pressure 26'may be automatically regulated as a function of the forces lapplied to the rolls 29 and 10.

In summary,'wben the crown of the backing roll 10, shown in FIGURE 1, changes during operation, or when a backing roll of a different crown is employed, the bow in the doctor back 12 is changed by varying the force applied by the bellows 26 by changing the air pressure therein. This changes the force applied at the center and the ends of the doctor back, normal to the plane of the doctor blade 13, land changes the bow in the doctor back to conform to the crown in the roll and obtain uniform blade pressure along the roll length.

Thus it will be seen that I have provided an improved doctoring assembly which meets the objectives and advantages above set forth. The mechanism is relatively inexpensive for commercial production and is capable of long continued operation without adjustment or attention. Further, the structure can be readily adapted to doctor backs of any commercial length and to bellows of dilferent capacities and tie rods of dilerent length will permit such adaptation.

' The drawings and speciiication present a detailed disclosure of the preferred embodiments of the invention, and it is to be understood that the invention is not limited -to the specific forms disclosed, but covers all modications, changes and alternative constructions and methods falling within the scope of the principles taught by the invention.

I claim as my invention:

1. In a doctoring assembly comprising in combination,

a backing roll for supporting a travelling web,

a doctor back adapted for supporting a doctor blade in close running pressure relationship with the web,

a tie rod means extending along the length of the doctor 'back and secured to the ends thereof,

Ia fluid pressure bellows intermediate the ends of the back and positioned between the back and rod for applying a force to the back laterally thereof,

a saddle member between the rod and bellows,

the improvement wherein the combination includes means connected between the bellows and back preventing tipping of the bellows and saddle member.

References Cited UNITED STATES PATENTS 865,488 9/ 1907 Graham 52-724 2,319,303 5/ 1943 Crawford 52291 2,698,020 12/1954 Phane 52--641 3,060,843 10/1962 Moore et al. 100--162 3,087,185 4/ 1963 Washburn 15-25651 3,122,090 2/ 1964 Binkowski 100-158 3,134,126 5/1964 Phillips 15-256.51 3,163,878 1/ 1965 Smith et al. 15-25651 FOREIGN PATENTS 178,455 5/ 1954 Austria.

ALFRED L. LEAVITI, Primary Examiner.

J. H. NEWSOME, Assistant Examiner. 

